CLASSIFICATION, LITHOLOGIC CALIBRATION, AND STRATIGRAPHIC SUCCESSION OF SEISMIC FACIES OF INTRASLOPE BASINS, DEEP-WATER GULF-OF-MEXICO

Seismic facies in Gulf of Mexico intraslope basins reflect the interpl ay of a variety of deepwater depositional processes and the evolution of accommodation space on the slope. This interplay of processes resul ts in a transition from an early, sand-prone ponded basin-fill success ion (ponded facies assemblage) to a later shale-prone, slope-bypass su ccession (bypass facies assemblage). Convergent-baselapping facies in combination with localized chaotic and draping facies dominate the pon ded facies assemblage. Stratigraphic relationships among these three u nits illustrate how fill-and-spill depositional processes occur within ponded-basin accommodation space. Convergent-thinning facies with wid espread chaotic and draping facies dominate the bypass facies assembla ge. These units represent filling of different types of slope accommod ation space. The transition from ponded to bypass facies assemblages c an be sharp or gradational over hundreds of meters. Transitions occure d across the central Gulf of Mexico during the late Pliocene between 2 .0 and 1.8 Ma, and in the early Pleistocene between 1.2 and 1.0 Ma. Ne arly synchronous transitions throughout basins in the upper to middle slope suggest that increased sediment supply, resulting from a second- order sea level fall, and capture of large drainage areas by the Missi ssippi River during the Pleistocene are the primary controls on develo pment of this large-scale stratigraphic architecture.